I'm hoping Guild Hunts will fill that role by giving lots of money and XP for completing them. You'll have to go to a certain area and fight much stronger versions of enemies. I'm thinking they'll be repeatable so you can get money and XP over and over again but I'm still deciding on that. Dimensional Dungeons sort of fill this role right now since you get more XP from the monsters. I might end up making these more difficult and more rewarding for going through them without leaving. There's also a chest in them with random loot but no equipment in the loot table. For special one time bosses I'll likely add some sort of equipment reward that can only be gotten from beating them.
Thanks for the suggestion.